Field of the Invention
The present invention relates to an image forming apparatus suitable for transferring image data used for image formation, and a program therefor.
Description of the Related Art
In recent years, an image forming apparatus such as copying apparatus or multi-function apparatus mounts thereon an image processing integrated circuit such as application specific integrated circuit (ASIC), in which image data to be printed, such as image data of reference colors of C (cyan), M (magenta), Y (yellow), and K (black), is temporarily developed in a main memory and then the image data of each print (each color) is read from the main memory by a direct memory access controller (DMAC) in response to an image request from an engine to be DMA-transferred to the engine.
Along with an increase in colors, the amount of image data to be transferred increases according to the number of increased colors. There is disclosed a technique for more rapidly transferring image data of more colors while restricting cost also when the amount of image data to be transferred increases along with an increase in colors (see JP 2011-073259 A, for example).
The copying apparatus described in JP 2011-073259 A reads the image data of the reference colors CMYK from the main memory by the DMA controllers (13C to 13K) and outputs it to the engines (8C to 8K) via the respective line FIFO. The copying apparatus according to JP 2011-073259 A reads the image data of a special color from the main memory by the DMA controllers for CMYK to be written into a page memory by a page memory write control unit before reading the image data of the reference colors CMYK at the first page and at an interval to read the image data of the reference colors CMYK between a previous page and a next page after the second page. The image data written into the page memory is read by a page memory read control unit to be output to an engine for special color (8C1).
With the technique described in JP 2011-073259 A, there are provided four DMA controllers for the colors CMYK in total, and image data of a fifth special color is distributed and transferred by the four DMA controllers thereby to achieve higher speed in data transfer (FIG. 5 in JP 2011-073259 A). However, JP 2011-073259 A does not describe how to control the four DMA controllers, or particularly a control method for distributing one color into the four DMA controllers.
For distribution and control in a typical control method, the CPU activating the DMA controllers needs to previously divide a size of image data on a main memory and to set an address and a size of the divided image data. The CPU needs to process a notification of transfer completion per DMA controller, which increases the CPU processing or the software processing.